Question

Carbon and silicon, elements used as the basis of biological life and synthetic computing, respectively, have some similar chemical properties. Which of the following describes a difference between the two elements? A. Carbon has a smaller atomic radius than silicon. B. Silicon has a smaller atomic radius than carbon. C. Carbon has fewer valence electrons than silicon. D. Silicon has fewer valence electrons than carbon.

Short answer

A. Carbon has a smaller atomic radius than silicon.

Step-by-step solution

- Analyze the Properties of Carbon

Carbon (C) is a non-metal element with an atomic number of 6. It has 4 valence electrons and forms a variety of compounds. Its atomic radius is approximately 70 pm (picometers).

- Analyze the Properties of Silicon

Silicon (Si) is a metalloid element with an atomic number of 14. It also has 4 valence electrons, similar to carbon. Its atomic radius is approximately 110 pm.

- Compare Atomic Radii

Comparing the atomic radii of carbon and silicon, carbon has a smaller atomic radius (70 pm) compared to silicon (110 pm). Therefore, option A is a correct difference: Carbon has a smaller atomic radius than silicon.

- Compare Valence Electrons

Both carbon and silicon have the same number of valence electrons, which is 4. Therefore, options C and D can be ruled out, as neither one has fewer or more valence electrons than the other.

- Eliminate Incorrect Options

Since it is established that carbon has a smaller atomic radius (eliminating option B) and both elements have the same number of valence electrons (eliminating options C and D), the correct answer is option A.

Key concepts

Atomic Radius

The atomic radius of an element refers to the size of its atoms, specifically the distance from the nucleus to the boundary of the surrounding cloud of electrons. Understanding this concept is crucial when comparing different elements like carbon and silicon.

Carbon, with an atomic number of 6, has an atomic radius of approximately 70 picometers (pm). On the other hand, silicon, with an atomic number of 14, has a significantly larger atomic radius of around 110 pm. This difference arises because silicon has more electron shells compared to carbon. More shells mean that the outermost electrons are further away from the nucleus.

So, in summary:

• Carbon: Atomic radius ≈ 70 pm
• Silicon: Atomic radius ≈ 110 pm

Thus, we can conclude that carbon has a smaller atomic radius than silicon.

Valence Electrons

Valence electrons are the electrons found in the outermost shell of an atom and are crucial in determining how an element will react chemically with other substances. Both carbon and silicon have the same number of valence electrons, which is 4. This similarity in valence electrons means that both elements can form four bonds with other elements, making them versatile in forming compounds.

For example, carbon forms strong covalent bonds and is a fundamental component of organic molecules, critical for life. Silicon, meanwhile, is essential in materials like glass and semiconductors due to its similar bonding properties. However, it's important to note:

• Carbon: 4 valence electrons
• Silicon: 4 valence electrons

Therefore, when it comes to valence electrons, neither carbon nor silicon has more or fewer than the other.

Element Comparison

Comparing elements like carbon and silicon can help us understand why they behave differently despite some similarities. Here are the key points when comparing these two elements:

1. Atomic Structure:
Carbon has 6 protons, and silicon has 14 protons. The number of protons affects the elements' physical and chemical properties.

2. Atomic Radius:
As mentioned earlier, carbon has a smaller atomic radius (70 pm) compared to silicon (110 pm). This smaller radius means carbon atoms pack closer together in compounds than silicon atoms.

3. Chemical Bonding:
Both elements can form four bonds due to their 4 valence electrons. However, carbon tends to form more robust and complex structures. Silicon's larger size and additional electron shells make its bonds slightly weaker and more flexible.

4. Usage:

• Carbon: Fundamental in organic chemistry and biochemistry.
• Silicon: Integral in electronics and synthetic materials.

In conclusion, while carbon and silicon share some similarities, particularly in bonding capacity due to their valence electrons, they have significant differences, primarily in atomic radius and usage, influencing their roles in nature and technology.